Apparatus for driving tunnels



f M. F. KEMPER APPARATUS FOR DRIVING TUNNELS May 10, 1966 Filed May 23, 1963 4 Sheets-Sheet 1 INVENTOR. AJAXW ,@Mpgg M. F. KEMPER May 1o, 1966 APPARATUS FOR DRIVING TUNNELS 4 Sheets-Sheet P,

Filed May 25, 1965 IllIT-l May 10, 1966 M. F. KEMPER APPARATUS FOR DRIVING TUNNELS Filed May 25, 1963 4 sheets-sheet 5 "May 1 0, 1966 M F. KEMPER APPARATUS FOR DRIVING TUNNELS 4 Sheets-Sheet 4 Filed May 23 INVENTOR. MA Xl/I/' KEA/ADEQ ATTOA/E'Y United States Patent O 3,250,078 APPARATUS FOR DRIVING TUNNELS Maxwell F. Kemper, 3701 Overland Ave.,

Los Angeles, Calif.

Filed May 23, 1963, Ser. No. 282,771 8 Claims. (Cl. 61-85) This invention relates to a novel apparatus for driving tunnels. l

Apparatus of the type to which this invention relates is disclosed in my U.S. Letters Patent No. 2,997,853 issued August 29, 1961, and includes an elongate arched shield adapted to be progressively driven into the earth While shiftably supported by a series of extensible jacks or llegs likewise shiftably connected to the shield in order to be positioned best to support the shield for sustaining the load of the overburden in the operation of driving the tunnel.

It is desired in .driving tunnels with apparatus generally of the type above described to provide in the shield as much working room as possible in the area adjacent the face of the tunnel for the men and equipment required in digging the tunnel, and at the same time to position the supporting jacks at locations assuring that the shield safely will sustain the load of the overburden in different types of ground, without tilting, sinking or otherwise movingofr grade and so that accurate turns in the tunnel bore may be more readily made while remaining on grade.

It is an object hereof to provide novel tunnel driving apparatus which constitutes an improvement in this art in that it includes a particularly novel construction and relative arrangement of the shield and supporting jacks making it possible to achieve the advantages herein noted.

Further, it is an important object of this invention to provide novel tunnel driving apparatus'of the character described wherein the elongate shield is provided with aA pair of longitudinally extended tracks disposed in laterally spaced opposed relation on opposite sides of the longitudinal center line of the shield and adjacent the sides of the shield with a plurality of extensible ground-engageable jacks sl-idably joined to each track so that when the jacks are in engagement w-ith the ground, the shield may be moved or shifted relative to the jacks and be driven into the tunnel face. With this arrangement any one or more of the plurality of jacks on either side of the shield may be shifted to a location best suited to support the shield according to the nature of the ground in which the shield is being driven, or a plurality of jacks maybe grouped on one side of the shield at locations spaced 1ater ally and longitudinally relative to a group of jacks on the opposite side of the shield or the jacks otherwise disposed, and in all cases so that when any one jack is out of engagement with the ground, at least one other jack of the plurality on each side of the shield will serve as an adequate` support for the shield.

Another object of this invention is the provision of apparatus such as described wherein by reason of having the shield supported along each side of the longitudinal center thereof by a plurality of the jacks, it is possible to lengthen a jack on one side of the shield and to decrease the length of a jack on the other side of the shield in order to tilt or cant the shield to facilitate making a turn with the shield while maintaining it on grade and lwith the advantage of having other of the plurality of jacks on each side of thel shield afford adequate support forvthe shield.

An additional object 'of this invention is the provision of a tunnel driving apparatus such as described which in having a plurality of axially shiftable jacks close to each of the opposite side walls of the shield in rows extending longitudinally of the shield makes it unnecessary to provide a support or jack between the side jacks and thereby 3,250,078 Patented May 10, 1966 ice provides unobstructed working room at the face of the tunnel for men and equipment to the end that an eflicient and comparatively economical tunnel digging operation may be carried out.

It is another object of this invention to provide in tunnel driving apparatus of the character described novel stabilizing means associated with the plurality of extensible legs on jacks on each side of the shield for stabilizing the legs or jacks and holding them from being moved while the shield is being advanced in the formation of the tunnel, this stabilizing means permitting each leg or jack to be intentionally independently moved into positions best to support the shield but operating to prevent movement of the legs while the shield is being advanced.

Other objects and advantages of the invention will be hereinafter described or will become appa-rent to those skilled in the art, and the novel features of the invention will be defined in the appended claims.

Referring to the drawings:

FIG. 1 is a longitudinal sectional view of apparatus embodying the present invention with the elements thereof disposed for driving the shield into the face of the tunnel relative to the supporting jacks;

FIG. 2 .is a View similar to FIG. 1 showing the positions occupied by elements of the apparatus after the shield has been driven a full stroke into the face of the tunnel, and indicating by the dot-dash showing of one of the jacks how the jacks may be repositioned to prepare the apparatus for the next advance of the shield;

FIG. 3 is a transverse sectional view taken on the line 3--3 of FIG. 1;

FIG. 4 .is a front elevation showing the apparatus substantially in the same position as shown in FIG. 1; i FIG. 5 is an enlarged vertical sectional view of one of the extensible jacks for supporting the shield, showing schematically in association therewith the hydraulic circuit and control me-ans for each jack;

FIG. 6 is an enlarged detail view in section of the portion of the jacks to which the fluid lines are connected;

FIG. 7 is a fragmentary sectional view taken on the line 7 7 of FIG. 1, on an enlarged scale;

, FIG. 8 is a fragmentary view of a modified form of extensible jack for supporting the shield showing the latter in section and the jack in elevation; and

FIG. 9 is an enlarged fragmentary sectional view of the jack shown in FIG. 8 including the schematic view of the hydraulic circuit and manually operable pump means for extending and retracting the jack.

Apparatus embodying the present invention includes an elongate steel shield A of horseshoe shape adapted to be driven into the earth as shown in FIGS. 1 and 2, wherein F designates the face of the tunnel being formed.

The forward portion 1 of the shield is suitably reinforced preferably internally thereof an-d contains apparatusto be hereinafter described for driving the shield into the earth. The rear portion 2 of the shield is adapted to extend as a protect-ive shell over the tunnel lining or wall structure B that is erected progressively as the shield is advanced in the formation of the tunnel.

As here shown, the forward portion 1 of the shield is reinforced by means of longitudinally spaced arcuate plates 3 welded or otherwise fixed at their outer edges to interior surface of the shield and project-ing inwardly therefrom with their inner edges welded to arched ribs 4 extending to the lower edges of the sides of the shield. Just inside the downwardly and rearwardly inclined front end 5 of the shield are a series of triangular plates 6 welded to the inner surface of t-he shield and the foremost plates 3.

Means are provided for driving the shield into the earth and, as here shown, include four hydraulic rams 7 extended longitudinally of the interior of the front section 1 of the shield an-d securely fastened thereto in equidistantly spaced relation, there being a ram on each side of the top center portion of the sield and one on each side wall of the shield as will be apparent with reference to FIG. 3. The pistons 8 of the rams 7 extend rearwardly so as to contact the forward portion of the wall assembly B which serves as a solid base structure against which therpistons bear in actuating the rams 7 to advance the shield. Any suitable means, not shown, may be employed for supplying and controlling ythe application of hydraulic fluid for operating the rams '7, it being preferable, however, to operate these rams in the manner and by the means shown -in my co-pending application for patent, Serial No. 678,993, now Patent No. 3,138,933, issued June 30, 1964.

The wall or tunnel structure B, as here shown, may comprise a plurality of steel H-beams or ribs 9 that are erected in the rear of shell portion 2 of the shield as shown in FIGS. l and 2 with suitable lagging strips 10 installed between the beams. These beams and lagging strips are added to increase the length of the tunnel wall structure B as the shield is advanced.

If a concrete lining for forming a conduit in the tunnel is to be provided, the lagging strips 10 when uncovered by advancing the shield so that the rear shell port-ion 2 exposes a large portion of the structure B, may serve as the outer wall of a concrete form. However, in some instances, the structure B may be utilized as the supporting lining or wall of the tunnel and for the purpose of this description, 4it will be assumed that the foremost steel beam or rib 9 has been firmly installed. This rm installation of the foremost beam 9 is accomplished by use of jacks 11 as shown in FIG. 3, and 'the placing of base plates 12 under the beam whereby the structure B -is forced against the inner surface of the rear portion 2 of the shell and is firmly securedin place, with provision, however, for the shield to be advanced relative thereto. Brace members 13 are positioned longitudinally on the structure B in line with the pistons 8 of the rams 7 and against the foremost rib 9 engaged by the pistons, these braces beingsecurely attached in any suitable manner to the structure B so that a rm backing is provided for each piston to assure that the shield will be advanced upon actuation of the rams 7.

In accordance with the invention, a plurality of longitudinally shiftable and extensible supporting members -for the shield are located in a row in longitudinally spaced relation to one another against each side wall of the shield so as to leave a large unobstructed space between the sides of the shield at the face F of the tunnel for accommodating the digging apparatus and men required to dig the tunnel, While at the same time providing for a reliable support of the shield while the shield is advanced relative to the supporting members and at all other times during the operation of forming the tunnel.- A particular advantage of this arrangement of supports is that they may be moved one at a time vo1" otherwise into position best to brace the shield for supporting the over-burden in all types of ground, while at least one of the supports of the plurality on each side of the shield will be in shield supporting position during such movement of other of the supports. No center support is required for the shield while shifting the side supports as desired to prepare the shield for advance into the tunnel face, and no lundesirable tilting of the shield which was occasioned the shield. Obviously, more than two jacks may be provided on each side of the shield, the number of jacks required depending upon the size of the shield and the load it is required to sustain. When in supporting position, the jacks 15 and 16 are rested on blocks 14.

As a means for mounting the jacks 15 and 16 so that the shield may be shifted relative thereto in being driven into the tunnel face and so that the jacks may 'be shifted longitudinally of the shield to reposition them as supports, longitudinally extending track assemblies 17 are welded or otherwise secured to the upper part of the forward portion 1 of the shield in laterally spaced relation to the longitudinal center line of the shield. Each track assembly 17 includes a plate 18 welded to and depending from the inner surface of the shield and provided at its lower edge with a rail 19 welded thereto for supporting a carriage 20 having upperand lower -sets of rollers 21 which ride on the top of the rail and on the lower side of the rail. Each carriage 20 supports one of the jacks which is pivoted thereto asat 22. With this arrangement the shield may be shifted relative to the jacks While the latter support the shield. v

After an advance of the shield the jacks readily may be shifted longitudinally and repositioned as supports for the shield to prepare the shield for another advance into the tunnel face. The jacks 4may be swung on the pivotal connections thereof with the carriages 20 to out-of-theway positions when this is desired.

Means are provided for stabilizing the jacks or legs 15 and 16 and to prevent them from being moved as the shield is being advanced. For this purpose the forward jack or leg on each side of the shield has a pair of rods 20a connected as at 20h to the carriage 20 of the jack and extended therefrom rearwardly along opposite sides of the carriage 20 of the next adjacent jack. At their rear ends the rods 20a have a cross member 20c xed thereto and adapted to be secured by means of a hook 20d to a cable 20e.` This cable leads to a comealong 20f anchored as -at 20g to the structure B. The rods 20a are slidably supported on a cross member 20h fastened on the carriage 20 of the rearmost jack on each side of the shield. With this arrangement the rods 20a and cross member 20c comprise a frame or yoke D which embraces the plurality of jacks on each side of the shield yet permit free movement of the jacks the desired extent best for supporting the shield. As `shown `in FIGS. 1 and 7, whenthe jacks are positioned forwardly to support the shield for an advance into the tunnel face, the carriages 20 abut one another 4and as the foremost carriage and its jack are restrained by the yoke D, cable 20e and comealong20f, the plurality of jacks on opposite sides of the shield remain in upright position and are held against being moved as the shield is advanced relative thereto. The come-along 20e may be operated as required to release the cable to allow the foremost jack to be moved with the yoke D attached thereto. The comealong may be locked or tightened when the cable is taut and the jacks are forwardly positioned. The length of the yoke D is such that the rearmost jack or a plurality thereof, if desired, may be independently moved therein as required 'best to support the shield. Thus, the yokes D at each side of the assembly and its come-along, constitute -means for holding the forward jack against movement with the shield in an advance direction as well as for allowing independent longitudinal positioning of the respective rearward jacks.

Each of the jacks is constructed to be hydraulically extended and retracted whereby upon retraction from engagement with the ground, each jack may be shifted to thev location where it is desired to provide a `support for the shield and then extended into ground engaging position.

As here shown, each of the jacks 15 and 16 is of the same construction and includes a tubular body portion 23 the upper end of which ispivoted as hereinbefore noted as at 22 to one of the carriages 2l) and supports therein a fixed piston unit 24 and a movable cylinder 25. This cylinder extends from the lower end of the body portion 23 and is closed at its upper and lower ends by an annular member 26 and a closure 27 respectively. The piston 28 of the piston unit 24 is disposed between the closed ends of the cylinder 25 with the piston rod 29 'extending through the annular member 25. A -seal 30 carried by the member 26 forms a seal around the piston rod. i AS here shown, the piston rod 29 is made up of concentric tubular members 31 and 32 providing fluid passages 33 and 34, leading into cylinder above and below the piston 28 respectively. The upper end of the piston rod 29 is supported by a partition 35 which is fixed in the upper part of the body portion 23. Passages 33' and 34' in the partition 35 are arranged to register with the passages 33 and 34 in the piston rod. Hydraulic fluid under pressure when directed through the passages 33 and 33 Will enter the cylinder 23 above the piston 28 to cause the cylinder 25 to be retracted into the body portion 23, while fluid below the pistonis exhausted through passages 34 and 34 back to the source of hydraulic fluid under pressure. When hydraulic fluid under pressure is directed through the passages 34' and 34 into the cylinder 25 below the Ipiston 28 the cylinder will be extended while fluid above the piston will return to the source through passages 33 and 33'.

Each of the jacks 15 and 16 is controlled by a manually operable valve 36 mounted thereon and connected 'by means of a conduit 41 with the passages 33' and 33 in the jack. A similar conduit 42 connects the Valve 36 with the passages 34' and 34 in the jack. An intake manifold 39 and a return manifold 44 are mounted on each side wall of the shield and through flexible hose lines 40y and 43 respectively are connected to the valves 36 for the adjacent pair of jacks as indicated by the schematic showing in FIG. 5. As shown in FIGS. 1 and 2, the manifolds 39 and 44 are connected to intake and return conduits 45 and 46 which may be connected to any suitable source of hydraulic fluid under pressure, not

shown.

This arrangement of manifolds, conduits and control unit 24 and the cylinder 25 may be removed and replaced relative to the tubular body portion 23 of the jack, also so that an air blast may be applied to the interior of the body to clean out any foreign matter that may collect between the opposed wall-s of the body portion 23 and the cylinder 25. Accordingly, as best shown in FIG. 6, the piston rod 29 is held in an opening 47 in the partition 35 by means of a set screw 48, the removal of which makes it possible to remove the piston unit and the cylinder. With reference to use of an air blast for removing foreign matter, a normally plugged passage 49 leading through the partition 35 into the portion of the tubular body 23 below the partition provides for this operation. When the plug in the outer end of the passage 49 is removed Aan air blast may be directed into the body 23 through passage 49 for the purpose above stated.

A modified form of jack M embodying this invention which may be used in groups of two or more on each side `of the shield is shown in FIGS. 8 and 9, if desired, in place of the jacks 15 and 16. This jack is similar to the jacks 15 and 16 shown in FIG. 5, except for the use of the upper part thereof as a reservoir R for hydraulic fluid and the use of two manually operable pumps R1 and R2 mounted on the jack and operable for effecting extension and retraction of the jack. The pumps .R1 and R2 are provided with valves V1 and V2 respectively for controlling ow through the pumps. As 'the jack M is otherwise of the same construction as the jacks 15 and 16 and mounted on the vshield 5 in the same manner as the jacks 15 and 16, the same reference characters thatare applied to the jacks 15 and 16 and to the mounting means therefor are applied to the jack M.

The hydraulic circuit shown in FIG. 9 includes a supply line 50 leading from the reservoir R on the top of the jack M to the hand pump R1, which latter, when the valve V1 is in the position shown, may be operated to force fluid under pressure through a line 51 to passages 34' and 34 and below the piston 29, thereby extending the cylinder 25. The return fluid from above the piston 29 passes through passages 33 and 33', and line 53 leading to the pump R2, which latter, in view of the position of valve V2, will route the return fluid through return line 54 leading to the reservoir R. When the pump R2 is operated with the valve V2 turned to occupy the position of Vthe valve V1 shown in FIG. 9, fluid from supply line 50a leading from line 50 is pumped through line 53, passage 33' and 33 into the cylinder 25 above the piston 29, thereby retracting the cylinder 35 and causing return flow from below the piston through passages 34 and 34', line 51, valve V1. At this time the valve V1 is turned to occupy the same position -as the valve V2 in FIG. 9 so the return fiow will pass through lines 55 and 54 leading to reservoir R.

The apparatus of this invention includes a plurality of air operated rams 60 securely anchored to the shield S and provided with brackets 61 for supporting breast boards 62. These rams in being air operated rams will yield as the shield is advanced as the breast boards 62 are firmly held by the rams against the tunnel face F and thereby prevent cave-in of this face.

With reference to the foregoing description and accompanying drawings, it will be apparent that this invention provides a novel method of driving a tunnel into the earth with an elongate arched shield and a plurality of supports disposed on each side of the longitudinal center of the shield in such a manner that the Ishield is longitudinally movable relative to the ysupports and the supports may be longitudinally moved relative to the shield. In supporting each .side of the shield with a group of shiftable supports or jacks in accordance with this invention, the jacks may be shifted one or more at a time into positions best to support the shield but in all instances so that other of the jacks on each side `of the shield afford adequate support for opposite sides of the shield at all times. With this arrangement and method of disposing and shifting the jacks, a better positioning thereof for support of the shield in soft, wet or what is known as bad ground may be effected. Moreover, the length of each leg may be varied while it is in ground engaging and shield supporting position by extending certain jacks and retracting others. This will make it possible to tilt or cant the shield with a nicety so as to facilitate making accurate turns of the tunnel bore while remaining on grade. It it is desired to provide a greater number of jacks at a specific location on one side of the shield that is longitudinally spaced from a lesser number of jacks on the opposite side of the shield to compensate for bad ground or for any other purposes, this arrangement readily may be brought about. Not only will the foregoing advantages be afforded by utilizing a plurality of jacks on each side of the shield in the manner herein described, without use of a center jack, but greater working space is provided at the face of the tunnel to facilitate the operation of forming the tunnel.

While specific structural details have been shown and described, it should be understood that changes and alterations may be resorted to without departing from the spirit of the invention as defined in the appended claims.

I claim:

1. Apparatus for driving a tunnel comprising: an elongate, arched shield; means shiftably supporting said shield for axial movement; means for so moving said shield relative to said supporting means; said supporting means including a pair of longitudinally extended members carried by said shield adjacent the top of the shield in laterally opposed transversely spaced relation at opposite sides of the longitudinal center line of the shield; a plurality of extens-ible jacks depending from each of said longitudinally extended members for contact with the ground to support said shield; a track on each of said longitudinally extended members; and means individually shiftably connecting said plurality of said jacks with each of said tracks, with said jacks relatively disposed thereon so that when one of the plurality of jacks on either of said tracks is moved from contact with the ground, at least one other jack of said plurality on each track will be disposed in contact with the ground whereby said shield will be supported on opposite sides of said center line.

2. Apparatus for driving a-tunnel comprising: an elongate, arched shield; means shiftably supporting said shield for axial movement; means for so moving said shield relative to said supporting means; said supporting means including a pair of longitudinally extended members carried by said shield adjacent the top of the shield in laterally opposed transversely spaced relation at opposite sides of the longitudinal center line of the shield; at least two extensible and contractible shield supporting legs depending from each of said longitudinally extended members for contact with the ground beneath Vthe shield; and means shiftably connecting said legs with said longitudinally extended members so that said legs on each of said longitudinally extended members are disposed one ahead of the other subject to being shifted relative to one another and relative to said shield after said advance of said shield, to occupy a different shield supporting position while at least one leg on each of said longitudinally extended members remains in shield supporting position.

3. Apparatus for driving a tunnel comprising: an elongate, arched shield; means shiftably supporting said shield for axial movement; means for so moving said shield relative to said supporting means; said supporting means including a pair of longitudinally extended members carried by said shield adjacent the top of the shield in laterally opposed transversely spaced relation at opposite sides of the longitudinal center line of the shield; a pair of extensible and contractible shield supporting legs depending from each of said longitudinally extended members for contact with the ground beneath the shield; means shiftably connecting said legs with said longitudinally extended members so that said legs on each of said longitudinally extended members are disposed one ahead of the other subject to being shifted relative to one another and relative to said shield after said advance of said shield, to occupy a different shield supporting position while at least one leg on each of said longitudinally extended members remains in shield supporting position; and means embodied in each leg operable for moving the leg into and from Contact with the ground.

4. Apparatus for driving a tunnel comprising: an elongate, arched shield; means shiftably supporting said shield for axial movement; means for so moving said shield relative to said supporting means; said supporting means including a pair of longitudinally extended members carried by said shield adjacent the top ofthe shield in laterally opposed transversely spaced relation at opposite sides ofthe longitudinal center line of the shield; at least two extensible and contractible shield supporting legs de- 'of the other subject to being shifted relative to one an- `other and relative to said shield after said advance of said shield, to-occupy a different shield supporting position while at least one leg .0.1.1 $13911 `of said longitudinally extended members remains in shield supporting position; and anchoring means operatively connected with said legs to hold them against movement when said shield is moved axially.

5. Apparatus for driving a tunnel comprising: an elongate, arched shield; means shiftably supporting said shield for axial movement; means for so moving said shield relative to said supporting means; said supporting means including a pair of longitudinally extended members carried by said shield adjacent the top of the shield in laterally opposed transversely spaced relation at opposite sides of the longitudinal center line of the shield; at least two extensible and contractible shield supporting legs depending from each of said longitudinally extended members for contact with the ground beneath the shield; means shiftably connecting said legs with said longitudinally extended members so that said legs on each of said longitudinally extended members are disposed one ahead of the other subject to being shifted relative to one another and relative to said shield after said advance of said shield to occupy a different shield supporting position While at least one leg on each of said longitudinally extended members remainsin shield supporting position; and means embodied in each leg operable to vary the length of the leg while the leg is engaged with the ground.

6. Apparatus for driving a tunnel comprising: an elongate, arched shield; means shiftably supporting said shield for axial movement; means for so moving said shield relative to said supporting means; said supporting means including a pair of longitudinally extended members carried by said shield adjacent the top of the shield in laterally opposed transversely spaced relation at opposite sides of the longitudinal center line of `the shield; at least two lextensible and contractible shield supporting legs depending from each of said longitudinally extended members for contact with the ground beneath the shield; means shiftably connecting said legs with said longitudinally extended members so that said legs on each of said longitudinally extended members are disposed one ahead of the other subject to being shifted relative to one another and relative to said shield after said advance of said shield to occupy a different shield supporting position while at least one leg on each of said longitudinally extended members remains in shield supporting position; means embodied in each leg operable to vary the length of the leg while the leg is engaged with the ground; and anchoring means operatively connected with said legs adjacent the upper ends thereof to prevent movement of said legs during the axial movement of said shield.

7. Apparatus for driving a tunnel comprising: an elongate, arched shield; means shiftably supporting said shield for axial movement; means for so moving said shield relative to said supporting means; said supporting means yincluding a plurality of extensible and contractible legs depending from said shield for engagement with the ground; there being a plurality of legs arranged in a row on each -of opposite sides of the longitudinal center line of said shield; said rows of legs being adjacent the sides of said shield; means shiftably connecting each of said legs in each row with said shield; means engaged with the foremost leg of each row for restraining said foremost legs against axial movement during said advance of said shield; said last named means including a yoke connected to said foremost leg and embracing the legs rearwardly of the foremost legs; and means extending rearwardly from said yoke for releasably anchoring the yoke against movement.

8, Apparatus for driving a tunnel comprising: an elongate, arched shield; means shiftably supporting said shield for axial movement; means for so moving said shield relative to saidsupporting means; said supporting means including a pair of longitudinally extended members carried by said shield at the sides of the shield in laterally opposed transversely spaced relation at opposite sides of the longitudinal center line of the shield; a plurality of 9 10 extensible jacks depending from each of said longitudinal- 2,134,47 8 10/ 1938 Hollingsworth 61--85 1y extended members for contact with the ground to sup- 2,385,251 9/1945 Ayers 61-44 port said shield; a track o'n each of said longitudinally 2,997,853 8/1961 Kemper 61 85 extended members; and means individually shiftably connecting said plurality of said jacks with each of said 5 FOREIGN PATENTS tracks, with said jacks relatively disposed thereon so that 1,264,673 5 /1961 France. l when one of the plurality of jacks on either of said tracks 911,961 5 /195 4 Germany is moved from contact with the ground, at least one other jack of said plurality of each track will be disposed in con- 942384 5/1956 Germany' tact with the ground whereby said shield will be supported 10 1089710 9/1960 Germany "n opposl sldes of sald center Ime' CHARLES E. OCONNELL, Primary' Examiner.

References Cited by the Examiner EARL 1 'WITMER Examineh UNITED STATES PATENTS 5 R. A. STENZEL, Assimil: Examiner.

1,032,952 7/1912 Schnable 61--44 1 

1. APPARATUS FOR DRIVING A TUNNEL COMPRISING: AN ELONGATE, ARCHED SHIELD; MEANS SHIFTABLY SUPPORTING SAID SHIELD FOR AXIAL MOVEMENT; MEANS FOR SO MOVING SAID SHIELD RELATIVE TO SAID SUPPORTING MEANS; SAID SUPPORTING MEANS INCLUDING A PAIR OF LONGITUDINALLY EXTENDED MEMBERS CARRIED BY SAID SHIELD ADJACENT THE TOP OF THE SHIELD IN LATERALLY OPPOSED TRANSVERSELY SPACED RELATION AT OPPOSITE SIDES OF THE LONGITUDINAL CENTER LINE OF THE SHIELD; A PLURALITY OF EXTENSIBLE JACKS DEPENDING FROM EACH OF SAID LONGITUDINALLY EXTENDED MEMBERS FOR CONTACT WITH THE GROUND TO SUPPORT SAID SHIELD; A TRACK ON EACH OF SAID LONGITUDNALLY EXTENDED MEMBERS; AND MEANS INDIVIDUALLY SHIFTABLY CONNECTING SAID PLURALITY OF SAID JACKS WITH EACH OF SAID TRACKS, WITH SAID JACKS RELATIVELY DISPOSED THEREON SO THAT WHEN ONE OF THE PLURALITY OF JACKS ON EITHER OF SAID TRACKS IS MOVED FROM CONTACT WITH THE GROUND, AT LEAST ONE OTHER JACK OF SAID PLURALITY ON EACH TRACK WILL BE DISPOSED IN CONTACT WITH THE GROUND WHEREBY SAID SHIELD WILL BE SUPPORTED ON OPPOSITE SIDES OF SAID CENTER LINE. 